This invention relates to a process for making metal powders by batchwise or continuously electrolytically depositing metal particles in the pores of an anodic oxide surface of an anodized aluminum article followed by liberation of the thus deposited particles from the pores.
The art of surface treating and finishing of aluminum and its alloys is a complex and well developed art as evidenced by the texts of S. Wernick entitled Surface Treatment and Finishing of Aluminum and Its Alloys, Robert Draper Ltd., Teddington, England (1956) and G. H. Kissin, Finishing of Aluminum, Reinhold Publishing Corporation, New York. It is acknowledged that electroplating on aluminum requires extraordinary treatments to gain the necessary adhesion. The most familiar techniques for plating on aluminum are the zincating and anodizing processes. In the latter case which involves the plating over an anodic oxide layer formed on an aluminum substrate, the art has directed its efforts towards producing continuous electroplated coatings.
It has now been discovered that metal particles can be made by forming a discontinuous electroplated metal phase in the pores of unsealed anodized aluminum followed by liberation of the metal particles in the pores. This provides metal powders having a large surface area which can be used, for example, in metal powder coating compositions and the like.